The human spine is a flexible weight bearing column formed from a plurality of bones called vertebrae. Typically, a human spine includes thirty-three vertebrae, grouped into five regions (cervical, thoracic, lumbar, sacral, and coccygeal). Moving down the spine along the cranial-caudal direction, there are typically seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, five sacral vertebrae, and four coccygeal vertebrae.
The human vertebrae and associated connective elements are susceptible to a variety of diseases and conditions which may cause pain and disability. These diseases and conditions include spondylosis, spondylolisthesis, vertebral instability, spinal stenosis, degenerated intervertebral discs, and herniated intervertebral discs. The vertebrae and associated connective elements are also susceptible to injuries, including fractures and torn ligaments and further may endure surgical manipulations, including a laminectomy to relieve pressure on the spinal cord or nearby nerves.
The pain and disability related to the diseases and conditions often result from the displacement of all or part of a vertebra from the remainder of the vertebral column. Spinal fusion is a surgical procedure that aims to restore displaced vertebrae to their normal position and to fix those previously displaced vertebrae within the vertebral column. During a spinal fusion procedure, vertebrae are fused together so that relative motion no longer occurs between the fused vertebrae. Typically, a spinal fusion procedure includes removing a damaged intervertebral disc and restoring the spacing between the fused vertebrae, thereby eliminating the instability and removing the pressure on the neurological elements that are causing pain as a result of the disease or condition. The spinal fusion procedure can further include implanting an intervertebral implant between vertebrae, for example adjacent vertebrae, to recreate the natural intervertebral spacing between adjacent vertebrae, previously provided by the damaged and now removed intervertebral disc.
Intervertebral implants and techniques associated with implanting them typically involve an open surgical procedure. An open surgical procedure is any surgical technique where the size of an incision in a patient's body is sufficient to permit the surgical procedure to take place under the direct vision of the surgeon. In other words, the structures and tissues involved can be seen and touched, and they are directly exposed to the air. Open surgical procedures may results in higher cost, lengthy in-patient hospital stays and increased post-operative pain.
An alternative to an open surgical procedure is a minimally invasive surgical procedure, for example a surgical procedure that involves endoscopic techniques. A minimally invasive surgical procedure typically includes accessing the site of pathology through one or more small incisions, with the goal of protecting the integrity of intervening tissues. A minimally invasive surgical procedure may result in reduced post-operative pain, reduced post-operative recovery time, and damage to healthy tissue compared to an open surgical procedure.
Minimally invasive surgical techniques are particularly desirable for spinal and neurosurgical applications because of the need for access to locations deep within the body and the danger of damage to vital intervening tissues. For example, such minimally invasive techniques can be utilized for spinal discectomy, or removal of an intervertebral disc, and spinal fusion, in which two or more vertebrae are fused together to stop the motion between them.
However, in a minimally invasive spinal fusion procedure using an intervertebral implant, the size of the opening in the patient's body must be large enough to accommodate the largest dimension of the intervertebral implant. Additionally, the maximum dimension of the intervertebral implant may limit the approaches available to a surgeon for use during a minimally invasive spinal fusion procedure. These and other short comings of the prior art are addressed by the present disclosure.